Electronic control throttle body

ABSTRACT

An electronically controlled throttle body has a torque motor including a stator and a moving portion (a slider), and a throttle shaft which is rotated by the torque motor. A rack as a plurality of gear teeth is formed at the moving portion, and a gear which mates with the rack is disposed at the throttle shaft. By arranging the radius of the gear appropriately to the reciprocating range of the slider, the motion of the slider is transmitted to the throttle shaft effectively. Therefore, the electronically controlled throttle body, can efficiently transmit motion of the torque motor, including a linear type, to the throttle shaft with a simple structure.

TECHNICAL FIELD

This invention relates to an electronically controlled throttle bodywhich is driven by a motor.

BACKGROUND ART

FIG. 7 is a sectional view showing a structure of a conventionalelectronically controlled throttle body. The throttle body 1 has acircular bore 2 a at the center of a main body 2, and acircular-disc-shaped throttle valve 3 is disposed therein. The throttlevalve 3 is fixed with two screws 5, 5 to a throttle shaft 4 whichpierces the bore 2 a, and is free to rotate from the position to closethe bore 2 a to a full-open position being parallel to the center axisof the bore 2 a. The rotating range is 90 degrees at the maximum, and nomore range is needed.

A motor 6 is integrally attached to the throttle body 1, and the shaftof the motor 6 is integral with the throttle shaft 4. Here, by changingthe power supply direction, the throttle shaft 4 turns in the openingdirection or the closing direction.

A torque motor is adopted as the motor 6. In general, a torque motor hascharacteristics of having excellent responsiveness and high reliabilitysince there is no contact. The motor 6 of this kind generally has arotor to which a ring-shaped magnet is fixed, and controls a rotatingposition in accordance with changes of magnetic flux distribution formedby a coil and a magnetic path.

As mentioned above, with the throttle body 1, the rotating range of thethrottle valve to open and close the bore 2 a is 90 degrees at themaximum. For example, when an inclination of about 5 degrees is set atidling, the rotating range becomes about 85 degrees. Consequently, therotating range of the throttle valve 3 is 90 degrees or less. To driveand control within this range, the magnet is not needed over the wholecircumference. In addition, the magnet used for the rotor is expensivesince the magnetic flux density has to be high.

Therefore, a torque motor 10 utilizing segment type magnets was devised,as shown in FIG. 8. A rotor 11 of this figure is connected directly tothe throttle shaft 4 in FIG. 7. About two thirds of the circumference ofthe rotor 11 is covered by two segment type magnets 12, 12. Since themagnet is downsized by changing from a ring-shape to a segment type, thecost can be reduced. An air-gap is formed between the circumference faceof the magnets 12, 12 and a yoke 13. Another air-gap is formed betweenthe circumference face of the magnets 12, 12 and a core 14. A coil 15 isdisposed at the core 14.

Parts of the yoke 13 corresponding to the magnet 12, 12 are first andsecond magnetic sides 13 a, 13 b whose top end faces are arc-shaped.Similarly, a part of the core 14 corresponding to the magnet 12, 12 is athird magnetic side 14 a whose top end face is arc-shaped. Then, thesethree magnetic sides 13 a, 13 b, 14 a are located on the same arc.Further, a stator is constructed by the yoke 13, the core 14 and thecoil 15, and a moving portion is constructed by the rotor 11 and themagnets 12, 12.

When electric current is supplied to the coil 15, the rotor 11 rotatesaround the axis O, and the throttle valve 3 which is directly connectedto the rotor 11 opens and closes. The rotating direction of the rotor 11changes in accordance with the direction of the electric current whichpasses through the coil 15. With the above-mentioned torque motor 10,the rotating angle of the rotor 11 is about 120 degrees, because themagnets 12, 12 cover about two thirds of the circumference of the rotor11.

However, as mentioned above, since the rotating angle of the throttleshaft 4 is approximately between 85 degrees and 90 degrees, the use ofthe torque motor 10 in FIG. 8 is not efficient.

Further, the above-mentioned torque motor 10 has a characteristic thatthe torque generated at both ends is lower than the torque generated atthe center of the rotating range. This seems to be caused by magneticcircuit problems, such as the magnetizing angle of the magnet, themagnetic saturation of the magnetic poles, and so on. On the contrary,in a normal usage situation, the throttle valve 3 is operated withapproximately equal torque from the full-close position to the full-openposition. Therefore, it is desirable to obtain a flat torquecharacteristic. Further, considering freezing in the winter, it is moredesirable that the torque at the full-close position is the maximumtorque.

For efficiency, adopting a speed reduction mechanism which transmits therotating angle of the rotor 11 to the throttle shaft 4 via a speedreducer to reduce the angle has been considered. However, having aseparate speed reducing mechanism is not desirable since it increasesthe size of the throttle body. Further, the cost increases because thenumber of parts increases.

On the other hand, as shown in FIG. 9, adopting a linear type torquemotor 20 to obtain a flat torque characteristic has been considered. Thetorque motor 20 is disclosed in patent application No. 2000-4107 whichwas previously submitted by the same applicant as this application. Thetorque motor 20 shown in FIG. 9 has a first stator 21 shaped almost likea rectangle, a second stator 22 shaped like three sides of a shallowrectangle which is disposed with a gap 23 to the first stator 21, anelectromagnetic coil 24 which is disposed between the first stator 21and the second stator 22, a slider 25, and two magnetized members 26, 27which are attached to the slider 25. The magnetized members 26, 27 areplate-shaped magnets which have magnetic poles in the thicknessdirection (the vertical direction in FIG. 9), and disposed so that themagnetic polarities of the magnetized members 26, 27 which are adjacentto each other are opposite to each other.

The first stator 21 has two magnetic sides 21 a, 21 b, and the secondstator 22 has one magnetic side 22 a. These three magnetic sides arelocated in a line, and a gap 28 is maintained between the magnetizedmembers 26, 27 of the slider 25 and the magnetic sides 21 a, 21 b, 22 a.

With the linear type torque motor 20, a stator is structured by thefirst stator 21, the second stator 22 and the electromagnetic coil 24,and a moving portion is structured by the slider 25 and magnetizedmembers 26, 27. Then, in accordance with the direction of electriccurrent to the electromagnetic coil 24, the slider moves in bothdirections shown by the arrow.

Here, the actuating force applied to the slider 25 is almost constant nomatter where the slider 25 is positioned. Therefore, by transmitting themovement of the slider 25 to the throttle shaft 4, the rotating torquewhich is applied to the throttle shaft 4 can be almost constant.

However, to convert linear motion of the slider 25 to rotating motion ofthe throttle shaft 4, separate parts are needed and the structure iscomplicated.

The present invention is devised in consideration of the above-mentionedfacts, and the object is to provide an electronically controlledthrottle body which can efficiently transmit the motion of a torquemotor, including a linear torque motor, to a throttle shaft with asimple structure.

SUMMARY OF THE INVENTION

In order to achieve the above-mentioned object, the electronicallycontrolled throttle body of the present invention comprises a torquemotor which has a stator and a moving portion, and a throttle shaftwhich is rotated by the torque motor, wherein a plurality of gear teethis formed at the moving portion, and a gear which mates with theplurality of gear teeth is disposed at the throttle shaft.

Further, it is possible to adopt a structure such that the stator hasthree magnetic sides which are disposed approximately on a same locus,the moving portion is movable in two directions within a specific rangehaving two magnetized members which face the three magnetic sides of thestator, and the plurality of gear teeth of the moving portion is formedat the moving portion where the magnetized portion is not disposed.

Here, the moving portion can be formed by laminating a plurality of thinplates of ferromagnetic material. It is also possible to adopt astructure such that the three magnetic sides are located approximatelyin a line, the moving portion is a slider which reciprocates on a line,and the plurality of gear teeth is a rack which is formed at the slider.It is also possible to adopt a structure such that the three magneticsides are located approximately on an arc, and the moving portion is arotor which is rotatable in a range of less than 360 degrees. Here, boththe plurality of gear teeth of the rotor and the gear of the throttleshaft can be non-circular gears.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of an electronically controlled throttle bodystructure of the first embodiment of the present invention in which alinear type torque motor is adopted as driving means.

FIG. 2 is a view from A in FIG. 1 showing a stator, a moving portion andits surroundings.

FIG. 3 is an exploded perspective view showing around a slider and amagnetized member.

FIGS. 4( a) and 4(b) show a second embodiment of the present inventionutilizing a torque motor which has a rotor as a moving portion. FIG. 4(a) corresponds to FIG. 2 of the first embodiment, and FIG. 4( b)corresponds to FIG. 1 of the first embodiment.

FIG. 5 is an exploded perspective view showing a rotor and magnetizedmembers.

FIG. 6 explains how to determine pitch curve shapes of a non-circulardriving gear and a driven gear.

FIG. 7 is a sectional view showing a structure of a conventionalelectronically controlled throttle body.

FIG. 8 shows a structure of a conventional torque motor utilizingsegment type magnets.

FIG. 9 shows a structure of a conventional linear type torque motor.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 and FIG. 2 show the first embodiment of the present invention.FIG. 1 is a sectional view of an electronically controlled throttle bodystructure in which a linear type torque motor is adopted as drivingmeans. FIG. 2 is a view from A in FIG. 1 showing a stator, a movingportion and their surroundings.

With the structure of the linear torque motor 20 in these figures, thesame numerical note is given to the same part in FIG. 9. A slider 25 ofthe linear type torque motor 20 has guides 25 a, 25 a at both sideswhich are in rolling contact with rollers 29, 29 so as to maintain a gap28 (see FIG. 9).

On the opposite side of magnetized members 26, 27 of the slider 25, arack 25 b is formed as a plurality of gear teeth. A gear 30 which mateswith the rack 25 b is fixed to a throttle shaft 4.

FIG. 3 is an exploded perspective view showing around the slider 25 andthe magnetized members 26, 27. The slider 25 is constructed bylaminating a plurality of plates of ferromagnetic material, such assteel plates. When each thin plate is formed by press working, namely,by being cut out of a base thin plate, the rack 25 b can be formedsimultaneously. Therefore, gear cutting is not needed, and the rack 25 bcan be formed easily.

The slider 25 reciprocates within the movable range of the linear typetorque motor 20. Since the rack 25 b is mated with the gear 30, thethrottle shaft 4 rotates. Here, when the radius of the gear 30 isarranged so that the movable range of the slider 25 fully overlaps therotating range of the throttle shaft 4, the whole movable range of thelinear type torque motor 20 can be utilized effectively, and waste canbe avoided. Since the throttle shaft 4 rotates only up to 90 degrees,the gear 30 can be a sector gear.

As explained above, with the aforementioned embodiment, the linearmotion of the linear type torque motor 20 can be converted to therotating motion of the throttle shaft 4 with a very simple structure,and the linear type torque motor capacity can be fully used.

FIGS. 4( a) and 4(b) show a second embodiment of the present inventionutilizing a torque motor 10 which has a rotor as a moving portion. FIG.4 (a) corresponds to FIG. 2 of the first embodiment, and FIG. 4( b)corresponds to FIG. 1 of the first embodiment. The torque motor 10 hasthe same structure as explained in FIG. 8. While the throttle shaft 4 isdirectly connected to the rotor 11 in the prior art, the throttle shaft4 is disposed separately from the shaft 32 a of the rotor 32 in thisembodiment.

FIG. 5 is an exploded perspective view showing around a rotor 32 andmagnetized members 12, 12. The rotor 32 is constructed by laminating aplurality of thin plates of ferromagnetic material such as steel plates,and the shaft 32 a of the rotor pierces through the center holesthereof. At both sides of the rotor 32, the two magnetized members 12,12 are bonded and fixed. Then, a plurality of the gear teeth 32 b isformed at the portion of the rotor where the magnetized members 12, 12are not disposed. When the rotor 32 is cut out of a thin plate, theplurality of the gear teeth 32 b is simultaneously cut out and formed.Here, in this embodiment, the plurality of the gear teeth 32 b forms asector gear being a part of an oval gear whose pitch circle is avertically oriented oval 32 c.

A gear 33 which mates to the plurality of the gear teeth 32 b isattached to the throttle shaft 4. The gear 33 is a sector gear being apart of an oval gear whose pitch circle is a horizontally oriented oval33 a.

By adopting these oval gears, the throttle shaft 4 can be rotated withapproximately constant rotating torque from the full-close position tothe full-open position of the throttle valve 3. Further, by arrangingthe gear ratio appropriately, the whole movable rotating range of thetorque motor 10 can be efficiently utilized for the range of thethrottle valve 3 between the full-close position and the full-openposition. Furthermore, the structure is simple because the onlymodification to the prior structure is the oval gears 32 b and 33.Furthermore, the manufacturing cost is low because the plurality of gearteeth 32 b as one gear can be simultaneously formed when the rotor 32 isformed.

Although an oval gear is used in the above-mentioned embodiment, it isnot limited to this, and various kinds of non-circular gears can beused.

FIG. 6 explains how to determine pitch curve shapes of a non-circulardriving gear 41 and a driven gear 42. As shown in this figure, thecenter of the driving gear 41 is O2, the center of the driven gear 42 isO1, and both pitch curves of the driving gear 41 and the driven gear 42are in contact with each other at point P. Then, if the driving gear 41rotates clockwise (plus direction) by a small angle d θ2, and the drivengear 42 rotates counter-clockwise (minus direction) by a small angle dθ1, so that point P1 and point P2 are to be in contact with each other,the following equations hold.r1+r2=α  (1)r1·dθ1=r2·dθ2  (2)

On the condition that α=1, r1 and r2 are given by the equation (1) andequation (2) as follows.r1=(−dθ2/dθ1)/{1−(dθ2/dθ1 )}  (3)r2=1/{1−(dθ2/dθ1)}  (4)

Here, −d θ2/d θ1 represents an angular velocity ratio. Therefore, givingthe angular velocity ratio to the equation (3) and equation (4), theradiuses r1, r2 of pitch circles at that angle are determined.

Namely, the following equations hold between torque T(θ2) of the torquemotor 10 at the rotating angle θ2, and torque T(θ1) which is transmittedto the driven gear.

$\begin{matrix}\begin{matrix}{{T\left( {\theta\; 2} \right)} = {{T\left( {\theta\; 1} \right)} \cdot \left( {d\;{{\theta 2}/d}\;\theta\; 1} \right)}} \\{= {\left( {{r1}/{r2}} \right) \cdot {T\left( {\theta\; 1} \right)}}}\end{matrix} & (5)\end{matrix}$

Given T(θ2), r1 and r2 can be determined by the equations (3), (4) and(5).

Consequently, by drawing a diagram in which desired torque T(θ1) isplotted for every opening θ1 between full-close position and full-openposition of the throttle valve 3, the pitch curves of the driving gear41 and the driven gear 42 are obtained in accordance with the diagram.

Accordingly, when non-circular gears such as the oval gears are used forthe plurality of the gear teeth 32 b as the driving gear 41, and thegear 33 as the driven gear 42, regarding the relations between thethrottle shaft opening and the throttle shaft torque, it is possible,for example, that the shaft torque is maintained approximately constantregardless of the shaft opening, or it is also possible that the maximumtorque is obtained at the full-close position where the maximum load maybe applied.

In addition, as a matter of course, it is possible to adopt a circulargear instead of a non-circular gear, and reduce speed merely by the gearratio.

INDUSTRIAL APPLICABILITY

As explained above, the electronically controlled throttle body of thepresent invention comprises a torque motor which has a stator and amoving portion, and a throttle shaft which is rotated by the torquemotor, wherein a plurality of gear teeth is formed at the movingportion, and a gear which mates with the plurality of gear teeth isdisposed at the throttle shaft. Therefore, by arranging the gear ratioappropriately, the whole operating range of the torque motor can beutilized for the rotating range of the throttle shaft, and the torquemotor can be used efficiently. Further, by forming the plurality of thegear teeth at the moving portion, the increase of the number of parts isprevented, and the throttle body can be formed compactly.

Further, with the structure that the moving portion is formed bylaminating a plurality of thin plates of ferromagnetic material, theplurality of gear teeth is formed simultaneously at the time when themoving portion is formed. Therefore, cost reduction can be achieved bydecreasing machining process time. Further, since the thickness of theplurality of the gear teeth can be kept sufficient, the load applied tothe gear which mates with the teeth is distributed. Consequently, thedurability improves and the gear can be made of low-cost resin material.

With the structure having the three magnetic sides located approximatelyin a line, the moving portion is a slider which reciprocates on a line,and the plurality of gear teeth is a rack which is formed at the slider,the linear motion of the linear type torque motor can be converted tothe rotating motion of the throttle shaft with a simple structure.

With the structure having the three magnetic sides located on anapproximate arc, the moving portion is a rotor which is rotatable withinthe range of less than 360 degrees, and both the plurality of gear teethof the rotor and the gear of the throttle shaft are non-circular gears,the desired driving torque can be obtained from the full-close state tothe full-open state of the throttle valve.

1. An electronically controlled throttle body, comprising: a torquemotor which has a stator and slider; and a throttle shaft which isrotatable by said torque motor; wherein said slider has a rack of gearteeth, and said throttle shaft has a gear which mates with said rack ofgear teeth, and wherein said stator has three magnetic sides which aredisposed approximately on a same locus and located approximately in aline, said slider has two magnetized members which face the threemagnetic sides of said stator, said slider is adapted to reciprocate ona line in two directions within a specific range, and said rack of gearteeth of said slider is formed at a portion of said slider where saidtwo magnetized members are not disposed.
 2. The electronicallycontrolled throttle body according to claim 1, wherein said slidercomprises a plurality of thin plates of ferromagnetic material laminatedtogether.
 3. The electronically controlled throttle body according toclaim 1, wherein said rack of gear teeth is integrally formed with saidslider.
 4. The electronically controlled throttle body according toclaim 2, wherein each of said plurality of thin plates has across-section of said rack of gear teeth integrally formed therein. 5.The electronically controlled throttle body according to claim 1,wherein said gear of said throttle shaft is a sector gear.
 6. Theelectronically controlled throttle body according to claim 2, whereinsaid gear of said throttle shaft is a sector gear.
 7. The electronicallycontrolled throttle body according to claim 3, wherein said gear of saidthrottle shaft is a sector gear.
 8. The electronically controlledthrottle body according to claim 4, wherein said gear of said throttleshaft is a sector gear.
 9. The electronically controlled throttle bodyaccording to claim 1, wherein said gear of said throttle shaft is madeof a resin material.
 10. The electronically controlled throttle bodyaccording to claim 3, wherein said gear of said throttle shaft is madeof a resin material.
 11. The electronically controlled throttle bodyaccording to claim 3, wherein said gear of said throttle shaft is madeof a resin material.
 12. The electronically controlled throttle bodyaccording to claim 4, wherein said gear of said throttle shaft is madeof a resin material.
 13. The electronically controlled throttle bodyaccording to claim 5, wherein said gear of said throttle shaft is madeof a resin material.
 14. The electronically controlled throttle bodyaccording to claim 6, wherein said gear of said throttle shaft is madeof a resin material.
 15. The electronically controlled throttle bodyaccording to claim 7, wherein said gear of said throttle shaft is madeof a resin material.
 16. The electronically controlled throttle bodyaccording to claim 8, wherein said gear of said throttle shaft is madeof a resin material.